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Thursday, 21 February 2013

Back in 2010, when I was employed in building a series of giant pterosaur models for the University of Portsmouth and Royal Society, I painted the above image of several giant azhdarchids in flight for use on our display boards and advertising work (bonus sauropods can be seen playing in the water below the pterosaurs). The azhdarchids are meant to be a fairly close match for our models, and specifically the giant, 10 m wingspan jobby we suspended between Royal Festival hall and the neighbouring buildings:

Our 2010 exhibition, with BigQuetz at the topright. Two smaller giants follow behind it, with the giant Bamofo looking on. Pterosaur worker Michael O'Sullivan can be seen in the bottom left.

BigQuetz in all its 10 m span glory

Our giant model had a couple of goofs that I wish we could have avoided, but was far from the worst rendition of a giant pterosaur I've ever seen. Certainly, there was no doubting its enormous size, which was substantial enough to shade a gathering of people escaping the unusually intense London sun experienced in June/July 2010. Alas, impressive as it was, it's size proved to be problematic for transportation and storage purposes. For engineering reasons, the body and wings of our BigQuetz were constructed as a single, solid unit, which meant that it had to be transported on a long-base low loader and, after its display in London, finding places to store and display it proved very, very difficult.

The BigQuetz body and wing frame, with pterosaur workers for scale (I'm on the left, Dave Martill is on the right)

The upshot is that BigQuetz, after a short stint on display in the Netherlands, had to weather being stored outside the School of Earth and Environmental Sciences in the open campus of the University of Portsmouth. Dave Martill, our pterosaur model wrangler, tried repeatedly to offload the model to various institutions but, despite finding homes for the rest of our giant models, could not find anyone willing to take on the transportation costs and space requirements of BigQuetz, even if the model was otherwise theirs for the taking. We were all very aware that BigQuetz was vulnerable in being stored in this way and, indeed, the ravages of weather and occasional shunts around were begging to take a toll on its more delicate aspects. But, as is often the case, the biggest problem was protecting it from people. It was only a matter of time before someone found BigQuetz and started fooling about with it, and thus inevitable that it would be found, one day, with significant damage.

Sadly, that very day arrived at the turn of this year, when University of Portsmouth staff found the BiqQuetz head had been smashed in by unknown individuals (sadly, I don't have any photos to show of this). It seemed that the damage was well beyond repair, and the BigQuetz story was brought to a close when the model was chopped up and disposed of. It's a terrific shame that our model should meet such an inauspicious end, and particularly stings because I personally experienced the many hours of work that were poured into its creation, often by volunteers, and know of the craftsmanship that went into its production, particularly on its aluminium frame. Plus, I find it hard to rationalise its demise being caused by anything other than a stupid stunt pulled by bored delinquents, seeing as its location on campus was not conducive to being accidentally damaged by university staff. Some consolation can be found in the fact that our other models have found homes elsewhere, and are hopefully being looked after, but it still seems a tremendous waste. Hey ho. RIP BigQuetz, we hardly knew ye. Or whatever people say about this sort of thing.

Friday, 8 February 2013

It's been a bit pterosaur-light around these parts since I opened the blog in November, with dinosaurs dominating most posts. This week, to start setting things right, we're returning to the warm, leathery-winged bosom of pterosaurs, with a painting from 2010 showing two of the most famous ornithocheirid pterosaurs, Anhanguera santanae (on the left) and Ornithocheirus mesembrinus (right). These Brazilian pterosaurs are both from the Lower Cretaceous Santana Formation, a fossil site renowned for its excellent, three-dimensionally preserved vertebrate fossils. Pterosaurs are the most common tetrapods in this unit, and ornithocheirids are a well known component of that fauna. In fact, they're probably the most extensively documented pterosaurs from the Santana, in part because of the thorough and beautifully illustrated descriptions by Peter Wellnhofer, including those for specimens of Ornithocheirus and Anhanguera (Wellnhofer 1987; 1991).

Cock of the slight awkward walk: Ornithocheirus. mesembrinus out for a stroll, possibly trying to accentuate it's bottom. Perhaps it works out.

Ornithocheirids are unusually proportioned pterosaurs, bearing extremely robust and long wings, enormous heads but tiny bodies and legs. Only other ornithocheiroids, particularly members of Pteranodontia and (to a lesser extent) Istiodactylidae can boast similar proportions. These forms are considered closely related by some (e.g. Unwin 2003), suggesting that their unusual bauplan developed only once, and was taken to extremes by members of Ornithocheiridae and Pteranodontia. In all likelihood, this evolutionary emphasis on increasing the size of the wings and head reflects adaptations for long soaring flight over seas and oceans, while retaining long jaws to grab pelagic prey. This group of ocean-soaring pterosaurs also includes Nyctosaurus, which may be one of the most effective soaring animals to have ever lived. Nyctosaurus also achieves the accolade of being the cover star of my book, which I'm sure it would be much more excited about.

Two cowardly Anhanguera santanae, being cowardly.

The painting here shows a few ornithocheirids striding around, an activity that probably wasn't their favourite pastime. Their short trunk skeletons and hindlimbs make for very disproportionate frames, and their forelimbs are probably at the limit of being useful in terrestrial locomotion, beyond simply preventing them from falling over. The pair of Anhanguera on the left are clearly somewhat wary of the larger Ornithocheirus, but it's worth mentioning that they're hardly small. The wingspan of A. santanae is estimated at 4.15 m, which is fairly middling for a Cretaceous pterosaur, but dwarfs the largest flying animals we have today with their piddling 3 m wingspans. Ornithocheirus mesembrinus, by contrast, is one of the largest ornithocheiroids known with an estimated wingspan of 6 m (this, of course, contradicts what Kenneth Branagh told us in Walking with Dinosaurs, but evidence for Ornithocheirus, or any ornithocheirid for that matter, spanning 10 m has yet to be presented). The only ornithocheirid that may have intimidated O. mesembrinus was Coloborhynchus capito, which may have spanned up to 7.25 m (Martill and Unwin 2012), gigantic proportions comparable to those of the largest Pteranodon. Accordingly, when Ornithocheirus wanted to walk or fly somewhere, Anhanguera moved out of its way.

And that will have to do today, I'm afraid. I've already gone on too long, and I'm much too busy to say anything about other things that are relevant here: colour choices, ornithocheirid rostral structure, ornithocheirid taxonomy and many other things. Perhaps another time, then.

Sunday, 3 February 2013

Is it just me, or are stegosaurs not quite as popular as they used to be? Stegosaurs are iconic dinosaur species that, like tyrannosaurs and ceratopsids, have been drawn to death by generations of palaeoartists eager to capture their freakishly weird anatomy, but they don't seem to be quite the mainstay of dinosaur pop culture that they used to be. I could be wrong, but it seems that other dinosaur taxa, primarily feathery, near-birdy things, have take a share of the stegosaur limelight. Perhaps stegosaurs, and particularly Stegosaurus, are just a so familiar now that we've become a bit blasé about them. I know I certainly have, so I've not sketched or painted one in years. It was only in revisiting them for this piece that it struck me how freakin' weird stegosaurs are, even in this world of therizinosaurs, mononykosaurs and four-winged microraptors. The front of their bodies clearly belong to relatively small or medium-sized animals, but evolution thought it would be fun to give them hindquarters borrowed from an large elephant or small sauropod. Supporting the dainty head and neck is a set of seemingly well-engineered but overly-short forelimbs, which force their spinal columns into high, curving arches to span the height discrepancy between each limb set. And then there's the osteoderms, shaped into broad plates or spikes, which sit along their backs and may turn the distal end of the tail into a morning star. Stegosaurs make feathery maniraptorans look positively boring.

For this painting, I wanted to show a stegosaur - specifically the Upper Jurassic Morrison Formation species Stegosaurusstenops - with some real character, looking like it had lived a hard life in an unforgiving climate and surrounded by extreme and frequently dangerous animals. For this reason, I chose a rarely depicted, more or less head on aspect for the painting, thus bringing its tiny head to the fore, allowing us to see its face without forgetting that the body behind it was large and powerful. I imagine that standing next to a big stegosaurs should be like standing next to any big, unfamiliar animal. It may not eat you, but the feeling that we're a small, inferior species, and that the 6 tonne animal next to us has absolute right of way, will never disappear. There also seemed to be a lot that could be done with its appearance. Stegosaurus was a large enough animal that they were probably fairly long-lived, and would accumulate decades of wear-and-tear on their hides. Thus, I depicted his very imperfect skin with an extremely washed-out but high contrast colour scheme, in efforts to enhance his battered appearance. Fossil evidence also came into play with creating a history for this animal, as we have good evidence that stegosaur osteoderms were occasionally subject to extreme damage in life, perhaps because they were bitten by predators or, in the case of their defensive tail spines, winged into the side of assailants with enough force to break their tips (Carpenter et al. 2005). With this in mind, my stegosaur has a number of broken plates along its back, this animal having seen off its fair share of aggressors. At one point, he was also going to be depicted drooling long strands of spittle through heat-stress, but the effect wasn't quite in keeping with his posture, so I took a napkin to his beak and tidied him up (see detail, below).

I also thought it might be fun to play with the scaly depiction of stegosaurs a bit, decking the thagomizer out with a set of long, bright filaments. Excellent skin impressions from Morrison stegosaurs (possibly even from Stegosaurus itself, if the assessment of stegosaur taxonomy by Maidment et al. [2008] is correct)reveal that their bodies were covered, probably mostly, in typically archosaurian pebbly scales (Christiansen and Tschopp 2010). This integument is exactly what we would expect from a large ornithischian in a warm climate. As with many dinosaurs, their scales are of variable size across the body, with long rows of large (20 mm wide) scales stretching across the dorsal regions and smaller scales lining the belly (see image, below). By analogy with modern 'naked' mammals however, I wondered if some scaly dinosaurs would retain small regions of fuzziness from their ancestors for specific functions. The bushy tails, ear tufts and eyelashes of naked mammals are good analogues here. In this case, my stegosaur's thagomizer isn't bristly to swat flies as are the hairy tail tips of mammals, but to advertise its spikes to marauding predators, and make them think twice about attempting an attack. Further analogy can be made here with the striking colours of many poisonous or otherwise well defended animals: camouflage is thrown to the wind in favour of making themselves unmistakeable to predators, letting them know to think twice about attacking them. Additional uses for fuzzy thagomizers may be sociosexual display, dusting hard to reach shelves and corners or, perhaps for defensively tickling they way out of hairy situations (hat tip to Spike Ekins and Simon Clabby for the latter).

And speaking of patchy filament distribution, I also gave this guy eyelashes, but you can't really see them in all the shadow I then layered over the top. Eyelashes may seem very odd things to put on dinosaurs, but they are common features of animals that have fuzzy ancestors. Numerous bird species have specially adapted feathers which are functionally analogous to mammal eyelashes, for instance. At least hornbills, secretary birds, seriemas, parrots, roadrunners and ostriches bear them, which serve to trigger blinking when touched (as in mammals) and, in some species, shade the eye. Eyelashes are also frequently retained in mammals that have mostly or entirely lost their fur: elephants, rhinos, hippos, you, and others. Thus, it seems quite plausible that many dinosaurs and other ornithodirans had eyelash-like filaments, and that some scaly dinosaurs will have held onto them.

Right, that's a reasonably concise post for these parts, and will have to do for now: I need to get going with a big palaeoart project that will, coincidentally, also require some consideration of ornithodiran eyelashes. If I'm allowed, there may even be some bits of it being posted here before any of us are too much older.

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Who is this 'Mark Witton' chap?

Dr Mark Witton is a palaeontologist and palaeoartist, affiliated with the University of Portsmouth, UK. My technical research is focused on pterosaurs - Mesozoic flying reptiles - but my artwork has introduced me to a wide array of different fossil animals that are just as interesting. I work as a freelance author, consultant and artist: check out my work at MarkWitton.com, follow me on Twitter @MarkWitton, and browse my books here. Contact me at wittonprints[at]gmail.com. Due to volume of email I can't always reply to messages, but I do my best.